5K Time Calculator
Predict your 5K race time from a recent training effort. Enter your current pace (minutes per kilometer) and the distance of the training run. The calculator uses the Riegel formula — a commonly used method for race performance prediction — to extrapolate an expected 5 kilometer time.
This tool is helpful for runners planning race pacing, setting realistic goals, or tracking progress over time.
How it works
The calculator applies the Riegel formula: T2 = T1 × (D2 / D1)^1.06 , where T1 is your time for the training distance D1, and T2 is the predicted time for distance D2 (5 km). Using your current pace (min/km) we compute T1 = pace × D1, then predict T2 for 5 km.
T2 = T1 × (5 / D1)^1.06Example
If you ran 10 km at an average pace of 5:00 min/km, your total time for that run is 50 minutes. Using the Riegel formula, the predicted 5K time is:
T1 = 50 min (10 km × 5 min/km)
T2 = 50 × (5 / 10)^1.06 ≈ 50 × 0.48 ≈ 24.0 min → 24:00
How to use
- Enter your current average pace in minutes per kilometer (e.g., 4.5 for 4:30 min/km).
- Enter the distance of your recent training run in kilometers.
- The predicted 5K time will update automatically. Toggle charts to compare your training time and the predicted 5K time.
Frequently Asked Questions
Is the prediction exact?
No — it's an estimate. The Riegel formula provides a reasonable extrapolation based on endurance scaling, but actual race performance depends on fitness, pacing, terrain, weather, and race-day conditions.
What distance should I use for training data?
Use a recent, well-paced effort that reflects your current fitness. Time-trial efforts, tempo runs, or race results are good inputs. Very short or very irregular runs may give less reliable predictions.
Can I use pace in min/mile?
This calculator expects minutes per kilometer. Convert pace in minutes per mile to min/km before using the tool (1 mile ≈ 1.60934 km).
Notes for Coaches
Use this tool to quickly estimate race targets during training planning. Consider using multiple recent efforts and contextual information (interval fitness, long runs, fatigue) when setting race goals.